Forming device

ABSTRACT

A forming device that expands a metal pipe material to form a metal pipe includes: an upper die and a lower die that form a main cavity part forming a main body part of the metal pipe and a sub-cavity part forming a flange part of the metal pipe by surfaces thereof opposed to each other; and a shielding member that prevents foreign matter discharged from the main cavity part or the sub-cavity part from scattering, the sub-cavity part is extended to be opened to the outside of the die in a direction crossing an extending direction of the metal pipe material, and the shielding member is provided on a line in which the sub-cavity part extends in the expanding of the metal pipe material.

RELATED APPLICATIONS

Priority is claimed to Japanese Patent Application No. 2015-072089,filed Mar. 31, 2015, and International Patent Application No.PCT/JP2016/060482, the entire content of each of which is incorporatedherein by reference.

BACKGROUND Technical Field

Certain embodiments of the present invention relate to a forming device.

Description of Related Art

For example, a forming device described in the related art has beenknown as a forming device that forms a metal pipe having a pipe part anda flange part. The forming device described in the related art includes:a pair of an upper die and a lower die and a gas supply part thatsupplies a high-pressure gas that is a gas into a metal pipe materialheld between the upper die and the lower die. By combining the upper dieand the lower die together, a main cavity part for forming a pipe partand a sub-cavity part that communicates with the main cavity part toform a flange part are configured between the upper die and the lowerdie. In this forming device, a metal pipe material is expanded with thesupply of a gas into the metal pipe material in a case where the upperdie and the lower die are closed. Accordingly, the pipe part and theflange part can be simultaneously formed.

Specifically, parting surfaces (matching surfaces) of the upper die andthe lower die are formed in steps toward the center from the outside.When the upper die and the lower die are closed, a main cavity part as aforming space is formed between the parting surfaces at the center ofthe upper die and the lower die, and a sub-cavity part is formed as aforming space communicating with the main cavity part on a side of themain cavity part between the parting surfaces of the upper die and thelower die. The sub-cavity part is closed by the stepped parting surfacesof the upper die and the lower die and becomes a closed space in thedie.

SUMMARY

According to an aspect of the invention, there is provided a formingdevice that expands a metal pipe material to form a metal pipe, thedevice including: an upper die and a lower die that form a main cavitypart forming a main body part of the metal pipe and a sub-cavity partforming a flange part of the metal pipe by surfaces thereof opposed toeach other; and a shielding member that prevents foreign matterdischarged from the main cavity part or the sub-cavity part fromscattering, in which the sub-cavity part is extended to be opened to theoutside of the die in a direction crossing an extending direction of themetal pipe material, and the shielding member is provided on a line inwhich the sub-cavity part extends in the expanding of the metal pipematerial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a formingdevice according to one embodiment of the invention.

FIG. 2 is a transverse sectional view of a blow forming die and upperdie and lower die holding parts, taken along the line II-II of FIG. 1.

FIGS. 3A to 3C are enlarged views of the vicinity of electrodes. FIG. 3Ais a view showing a state in which a metal pipe material is held by theelectrodes. FIG. 3B is a view showing a state in which a sealing memberis brought into contact with the electrodes. FIG. 3C is a front view ofthe electrodes.

FIGS. 4A and 4B are diagrams showing a manufacturing step using theforming device. FIG. 4A is a diagram showing a state in which a metalpipe material is set in a die. FIG. 4B is a diagram showing a state inwhich the metal pipe material is held by the electrodes.

FIG. 5 is a diagram showing a manufacturing step following the steps inFIGS. 4A and 4B.

FIG. 6 is a diagram showing operations of the blow forming die and anupper die holder and a change in shape of the metal pipe material.

FIG. 7 is a diagram following FIG. 6.

FIG. 8 is a diagram following FIG. 7.

FIG. 9 is a schematic diagram showing a configuration of a main part ofa forming device according to another embodiment of the invention.

FIG. 10 is a schematic diagram showing a configuration of a main part ofa forming device according to a still another embodiment of theinvention.

DETAILED DESCRIPTION

Here, in the forming device, as described above, a sub-cavity partcorresponding to a shape (thickness and length) of a flange part becomesa closed space in the die. Accordingly, in a case where the flange partis formed with the supply of a high-pressure gas, there is a concernthat the flange part may deform, and a flange part having a desiredshape may not be formed.

Accordingly, in order to prevent the deformation of the flange part, itis considered that the sub-cavity part that is a forming space isexpanded to the outside of the die to make it open to the outside.However, in a case where the sub-cavity part is made open to theoutside, there is a concern that foreign matter such as fragments mayfly to the outside of the die and scatter to the surroundings in a casewhere it is assumed that a material itself has a low strength, and thusa metal pipe bursts due to a high-pressure gas in the die.

It is desirable to provide a forming device that can prevent foreignmatter such as fragments generated in a die from scattering to thesurroundings of the die.

According to the forming device, in the expanding and forming of themetal pipe material between the upper die and the lower die, foreignmatter such as fragments may be generated in the main cavity part or thesub-cavity part. In this case, the foreign matter moves outward in theextending direction of the sub-cavity part, crossing the extendingdirection of the metal pipe material. The foreign matter is preventedfrom advancing by the shielding member provided on the extending line ofthe sub-cavity part in the expanding of the metal pipe material.Accordingly, the foreign matter discharged from the main cavity part orthe sub-cavity part can be prevented from scattering to the surroundingsof the die.

Here, the shielding member may block the sub-cavity part from adirection in which the sub-cavity part is extended. In a case where sucha configuration is employed, the sub-cavity part is blocked from theextending direction of the sub-cavity part, and thus the foreign mattercan be securely prevented from scattering to the surroundings of the diewithout being discharged to the outside of the die.

In addition, the shielding member may be provided to be brought intocontact with a side surface of the upper die or the lower die and may bemoved with the movement of the upper die or the lower die to block thesub-cavity part from the direction in which the sub-cavity part isextended in a case where the die is closed. In a case where such aconfiguration is employed, a die holder holding the die can be used asthe shielding member and there is no need to provide a separateshielding member. In addition, in a case where the shielding member isprovided to be brought into contact with a side surface of the upperdie, in a state in which the shielding member is released from the die,the shielding member is separated upward from the lower die togetherwith the upper die. Accordingly, for example, in a case where the metalpipe material is inserted into the lower die or in a case where theformed metal pipe is detached from the lower die, the shielding memberdoes not become a hindrance.

Hereinafter, preferable embodiments of a forming device according to anaspect of the invention will be described with reference to thedrawings. In the drawings, the same or similar parts will be denoted bythe same reference signs, and overlapping description will be omitted.

Configuration of Forming Device

FIG. 1 is a schematic diagram of a configuration of a forming device.FIG. 2 is a transverse sectional view of a blow forming die, an upperdie holding part, and a lower die holding part, taken along the lineII-II of FIG. 1. As shown in FIG. 1, a forming device 10 that forms ametal pipe 100 (see FIG. 5) is provided with a blow forming die 13composed of a pair of a lower die 11 and an upper die 12, a lower dieholding part 91 for holding the lower die 11, an upper die holding part92 for holding the upper die 12, a driving mechanism 80 that moves atleast one of the lower die holding part 91 holding the lower die 11 andthe upper die holding part 92 holding the upper die 12 (here, upper dieholding part 92), a pipe holding mechanism 30 that holds a metal pipematerial 14 shown by the virtual line between the lower die 11 and theupper die 12, a heating mechanism 50 that energizes the metal pipematerial 14 held by the pipe holding mechanism 30 to heat the metal pipematerial, a gas supply part 60 for supplying a high-pressure gas (gas)into the metal pipe material 14 held and heated between the lower die 11and the upper die 12, a pair of gas supply mechanisms 40 for supplying agas into the metal pipe material 14 held by the pipe holding mechanism30 from the gas supply part 60, and a water circulation mechanism 72that forcibly cools the blow forming die 13 with water. In addition, theforming device 10 is provided with a controller 70 that controls drivingof the driving mechanism 80, driving of the pipe holding mechanism 30,driving of the heating mechanism 50, and gas supply of the gas supplypart 60.

The lower die 11 is fixed to a large base 15 via the lower die holdingpart 91. The lower die 11 is composed of a large steel block and isprovided with a recessed part 16 in an upper surface thereof (a partingsurface from the upper die 12). As shown in FIGS. 1 and 2, the lower dieholding part 91 holding the lower die 11 is provided with a lower dieholder 93 holding the lower die 11, a lower die holder 94 holding thelower die holder 93, and a lower die base plate 95 holding the lower dieholder 94, that are laminated in order from the top. The lower die baseplate 95 is fixed to the base 15. As shown in FIG. 1, lengths of thelower die holder 93 and the lower die holder 94 in an axial direction(lengths in the horizontal direction in FIG. 1) are almost the same asthat of the lower die 11 in the axial direction.

An electrode storage space lla is provided near each of right and leftends (right and left ends in FIG. 1) of the lower die 11, and a firstelectrode 17 and a second electrode 18 that are configured to advance orretreat in a vertical direction by an actuator (not shown) are providedin the electrode storage spaces 11 a. Recessed grooves 17 a and 18 ahaving a semi-arc shape corresponding to an outer peripheral surface onthe lower side of the metal pipe material 14 are formed in uppersurfaces of the first electrode 17 and the second electrode 18,respectively (see FIG. 3C). The metal pipe material 14 can be placed tobe well fitted in the recessed grooves 17 a and 18 a. In addition, infront surfaces of the first and second electrodes 17 and 18 (surfaces ofthe die in an outward direction), tapered recessed surfaces 17 b and 18b are formed such that the vicinities thereof are recessed at an angleinto a tapered shape toward the recessed grooves 17 a and 18 a,respectively. In addition, the lower die 11 has a cooling water passage19 formed therein and is provided with a thermocouple 21 inserted fromthe bottom at a substantially center thereof. This thermocouple 21 issupported movably up and down by a spring 22.

The pair of first and second electrodes 17 and 18 positioned in thelower die 11 constitute the pipe holding mechanism 30, and canelevatably support the metal pipe material 14 between the upper die 12and the lower die 11. The thermocouple 21 is just an example of thetemperature measuring unit, and a non-contact temperature sensor such asa radiation thermometer or an optical thermometer may be provided. Aconfiguration without the temperature measuring unit may also beemployed if the correlation between the energization time and thetemperature can be obtained.

The upper die 12 is a large steel block that is provided with a recessedpart 24 in a lower surface thereof (a parting surface from the lower die11) and a cooling water passage 25 built therein. As shown in FIGS. 1and 2, the upper die holding part 92 holding the upper die 12 isprovided with an upper die holder 96 holding the upper die 12, an upperdie holder 97 holding the upper die holder 96, and an upper die baseplate 98 holding the upper die holder 97, that are laminated in orderfrom the bottom. The upper die base plate 98 is fixed to a slide 82. Asshown in FIG. 1, lengths of the upper die holder 96 and the upper dieholder 97 in an axial direction (lengths in the horizontal direction inFIG. 1) are almost the same as that of the upper die 12 in the axialdirection. The slide 82 to which the upper die holding part 92 is fixedis suspended by a pressing cylinder 26, and is guided by a guidecylinder 27 so as not to laterally vibrate.

Similarly to the case of the lower die 11, an electrode storage space 12a is provided near each of right and left ends (right and left ends inFIG. 1) of the upper die 12, and a first electrode 17 and a secondelectrode 18 that are configured to advance or retreat in the verticaldirection by an actuator (not shown) are provided in the electrodestorage spaces 12 a. Recessed grooves 17 a and 18 a having a semi-arcshape corresponding to an outer peripheral surface on the upper side ofthe metal pipe material 14 are formed in lower surfaces of the first andsecond electrodes 17 and 18, respectively (see FIG. 3C), and the metalpipe material 14 can be well fitted in the recessed grooves 17 a and 18a. In addition, in front surfaces of the first and second electrodes 17and 18 (surfaces of the die in an outward direction), tapered recessedsurfaces 17 b and 18 b are formed such that the vicinities thereof arerecessed at an angle into a tapered shape toward the recessed grooves 17a and 18 a, respectively. Accordingly, in a case where the pair of firstand second electrodes 17 and 18 positioned in the upper die 12 alsoconstitute the pipe holding mechanism 30 and the metal pipe material 14is sandwiched between the upper and lower pairs of first and secondelectrodes 17 and 18 from the vertical direction, the metal pipematerial 14 can be surrounded such that the outer periphery thereoffirmly adheres well over the whole periphery. The fixing parts of therespective actuators moving the first electrode 17 and the secondelectrode 18 corresponding to a moving part up and down are held andfixed to the lower die holding part 91 and the upper die holding part92, respectively.

The driving mechanism 80 is provided with a slide 82 that moves theupper die 12 and the upper die holding part 92 so as to combine theupper die 12 and the lower die 11 together, a driving part 81 thatgenerates a driving force for moving the slide 82, and a servo motor 83that controls a fluid amount with respect to the driving part 81. Thedriving part 81 is composed of a fluid supply part that supplies a fluid(an operating oil in a case where a hydraulic cylinder is employed asthe pressing cylinder 26) for driving the pressing cylinder 26 to thepressing cylinder 26.

The controller 70 can control the movement of the slide 82 bycontrolling the amount of the fluid to be supplied to the pressingcylinder 26 by controlling the servo motor 83 of the driving part 81.The driving part 81 is not limited to a part that applies a drivingforce to the slide 82 via the pressing cylinder 26 as described above.For example, the driving part may be mechanically connected to the slide82 to directly or indirectly apply a driving force generated by theservo motor 83 to the slide 82. For example, a driving mechanism havingan eccentric shaft, a driving source (for example, a servo motor and areducer) that applies a rotating force for rotating the eccentric shaft,and a converter (for example, a connecting rod or an eccentric sleeve)that converts the rotational movement of the eccentric shaft into thelinear movement to move the slide may be employed. In this embodiment,the driving part 81 may not have the servo motor 83.

As shown in FIG. 2, an upper end surface of the lower die 11 and a lowerend surface of the upper die 12 are uneven. Specifically, the recessedpart 16 with a rectangular cross-sectional shape is formed at the centerof the upper end surface of the lower die 11, and the recessed part 24with a rectangular cross-sectional shape is formed at the center of thelower end surface of the upper die 12 to be opposed to the recessed part16 of the lower die 11.

The lower die holder 93 that constitutes the lower die holding part 91and holds the lower die 11 is provided with a recessed part 93 a with arectangular cross-sectional shape at a center of an upper end surface 93e of the rectangular parallelepiped. The lower die 11 is held such thatthe substantially lower half thereof is fitted into a recessed part 93 cwith a rectangular cross-sectional shape provided at the center of abottom surface 93 d of the recessed part 93 a. Spaces S1 and S2 arerespectively provided between protrusions 93 b at both sides that formthe recessed part 93 a of the lower die holder 93 and side surfaces ofthe substantially upper half of the lower die 11 that protrude higherthan the bottom surface 93 d of the lower die holder 93. Protrusions 96b of the upper die holder 96 to be described later proceed into thespaces 51 and S2 in a case where the blow forming die 13 is closed.

The upper die holder 96 that constitutes the upper die holding part 92and holds the upper die 12 is formed into a stepped block shape, inwhich the rectangular parallelepiped becomes smaller downward in astepwise manner, by forming two steps toward the lower side from theupper side at both sides of the rectangular parallelepiped. A recessedpart 96 a with a rectangular cross-sectional shape is formed at a centerof a lower end surface 96 d of the upper die holder 96, and the upperdie 12 is held to be housed in the recessed part 96 a. Accordingly,inner surfaces of the protrusions 96 b at both sides that form therecessed part 96 a of the upper die holder 96 are brought into contactwith the side surfaces of the upper die 12. In addition, the protrusions96 b protrude downward from the lower end surface of the upper die 12 bya predetermined length, and respectively proceed into the spaces 51 andS2 of the lower die holder 93 in a case where the blow forming die 13 isclosed. In addition, in a case where the blow forming die 13 is closed,the lower end surface (tip end surface) 96 d of the protrusion 96 b ofthe upper die holder 96 is brought into contact with the bottom surface93 d of the recessed part 93 a of the lower die holder 93, and stepsurfaces 96 e that form the protrusions 96 b at both sides of theprotrusions 96 b of the upper die holder 96 and are positioned above theprotrusions 96 b are brought into contact with the upper end surfaces 93e of the protrusions 93 b of the lower die holder 93.

As shown in FIG. 1, the heating mechanism 50 has a power supply 51,conductive wires 52 that extend from the power supply 51 and areconnected to the first electrodes 17 and the second electrodes 18, and aswitch 53 that is provided in the conductive wire 52. The controller 70controls the heating mechanism 50, and thus the metal pipe material 14can be heated to a quenching temperature (equal to or higher than an AC3transformation temperature).

Each of the pair of gas supply mechanisms 40 has a cylinder unit 42, acylinder rod 43 that advances or retreats in accordance with theoperation of the cylinder unit 42, and a sealing member 44 that isconnected to a tip end of the cylinder rod 43 on the side of the pipeholding mechanism 30. The cylinder unit 42 is placed and fixed on thebase 15 via a block 41. A tapered surface 45 is formed at a tip end ofthe sealing member 44 so as to be tapered. The tapered surfaces areformed into such a shape as to be well fitted in and brought intocontact with the tapered recessed surfaces 17 b and 18 b of the firstand second electrodes 17 and 18 (see FIGS. 3A to 3C). The sealing member44 is provided with a gas passage 46 that extends from the cylinder unit42 toward the tip end, specifically, through which a high-pressure gassupplied from the gas supply part 60 flows as shown in FIGS. 3A and 3B.

As shown in FIG. 1, the gas supply part 60 includes a high-pressure gassupply 61, an accumulator 62 that stores a gas supplied by thehigh-pressure gas supply 61, a first tube 63 that extends from theaccumulator 62 to the cylinder unit 42 of the gas supply mechanism 40, apressure control valve 64 and a switching valve 65 that are provided inthe first tube 63, a second tube 67 that extends from the accumulator 62to the gas passage 46 formed in the sealing member 44, and a pressurecontrol valve 68 and a check valve 69 that are provided in the secondtube 67. The pressure control valve 64 functions to supply, to thecylinder unit 42, a gas having an operation pressure adapted for thepressing force of the sealing member 44 with respect to the metal pipematerial 14. The check valve 69 functions to prevent the high-pressuregas from flowing backward in the second tube 67.

The controller 70 controls the pressure control valve 68 of the gassupply part 60, and thus a gas having a desired operation pressure canbe supplied into the metal pipe material 14. In addition, the controller70 acquires temperature information from the thermocouple 21 by thetransmission of the information from (A) shown in FIG. 1, and controlsthe pressing cylinder 26 and the switch 53.

The water circulation mechanism 72 includes a water tank 73 that storeswater, a water pump 74 that draws up and pressurizes the water stored inthe water tank 73 to send the water to the cooling water passage 19 ofthe lower die 11 and the cooling water passage 25 of the upper die 12,and a pipe 75. Although omitted, a cooling tower that lowers the watertemperature or a filter that purifies the water may be provided in thepipe 75.

Method of Forming Metal Pipe Using Forming Device

Next, a method of forming a metal pipe using the forming device 10 willbe described. FIGS. 4A and 4B show steps from a pipe injection step forinjecting the metal pipe material 14 as a material to an energizationand heating step for heating the metal pipe material 14 by energization.More specifically, FIG. 4A is a diagram showing a state in which themetal pipe material is set in the die. FIG. 4B is a diagram showing astate in which the metal pipe material is held by the electrodes. FIG. 5is a diagram showing a manufacturing step following the steps in FIGS.4A and 4B.

First, a metal pipe material 14 that is a quenchable steel type isprepared. As shown in FIG. 4A, the metal pipe material 14 is placed(injected) on the first and second electrodes 17 and 18 provided in thelower die 11 using, for example, a robot arm or the like. Since thefirst and second electrodes 17 and 18 have the recessed grooves 17 a and18 a, respectively, the metal pipe material 14 is positioned by therecessed grooves 17 a and 18 a. Next, the controller 70 (see FIG. 1)controls the pipe holding mechanism 30 to hold the metal pipe material14 by the pipe holding mechanism 30. Specifically, as in FIG. 4B, anactuator that allows the first and second electrodes 17 and 18 toadvance or retreat is operated such that the first and second electrodes17 and 18 positioned on the upper and lower sides, respectively, arebrought closer to and into contact with each other. Due to this contact,both of the end parts of the metal pipe material 14 are sandwichedbetween the first and second electrodes 17 and 18 from the upper andlower sides. In addition, due to the presence of the recessed grooves 17a and 18 a formed in the first and second electrodes 17 and 18, themetal pipe material 14 is sandwiched so as to firmly adhere over thewhole periphery thereof.

Next, as shown in FIG. 1, the controller 70 controls the heatingmechanism 50 to heat the metal pipe material 14. Specifically, thecontroller 70 turns on the switch 53 of the heating mechanism 50. Inthat case, electric power is supplied from the power supply 51 to themetal pipe material 14, and the metal pipe material 14 produces heat(Joule heat) due to the resistance present in the metal pipe material14. In this case, the measurement value of the thermocouple 21 ismonitored always, and based on the results thereof, the energization iscontrolled and the cylinder unit 42 of the gas supply mechanism 40 isoperated. Accordingly, both ends of the metal pipe material 14 is sealedby the sealing member 44.

FIG. 6 is a diagram showing operations of the blow forming die and theupper die holder and a change in shape of the metal pipe material. FIG.7 is a diagram following FIG. 6. FIG. 8 is a diagram following FIG. 7.

As shown in FIG. 6, the blow forming die 13 is closed with respect tothe metal pipe material 14 after heating. In this case, the protrusions96 b of the upper die holder 96 proceed into the spaces S1 and S2 of thelower die holder 93, and between the recessed part 16 of the lower die11 and the recessed part 24 of the upper die 12, a main cavity part MCwith a substantially rectangular cross-sectional shape is formed that isa gap for forming a pipe part (main body part) 100 a. With this,sub-cavity parts SC1 and SC2 that communicate with the main cavity partMC and are gaps for forming flange parts 100 b and 100 c arerespectively formed at both sides of the main cavity part MC between theupper end surface of the lower die 11 and the lower end surface of theupper die 12.

Here, the sub-cavity parts SC1 and SC2 between the upper end surface ofthe lower die 11 and the lower end surface of the upper die 12 extend tobe opened to the outside of the die. The sub-cavity parts SC1 and SC2are blocked from the outside by inner surfaces 96 f of the protrusions96 b of the upper die holder 96. The protrusions 96 b of the upper dieholder 96, blocking the sub-cavity parts SC1 and SC2 from the outside ofthe die, are operated such that foreign matter such as fragmentsgenerated when, for example, the metal pipe bursts in the die isprevented from advancing out of the die through the sub-cavity parts SC1and SC2 and from being discharged. Accordingly, the upper die holder 96having the protrusions 96 b also functions as a shielding member.

In this state, that is, in a state before the blow forming die iscompletely closed, the metal pipe material 14 is fitted in the maincavity part MC. In a state in which the metal pipe material is incontact with the bottom surface of the recessed part 16 of the lower die11 and the bottom surface of the recessed part 24 of the upper die 12, ahigh-pressure gas is supplied into the metal pipe material 14 by the gassupply part 60 to start blow forming.

Here, since the metal pipe material 14 is softened by being heated at ahigh temperature (about 950° C.), the gas supplied into the metal pipematerial 14 is thermally expanded. Therefore, for example, with the useof compressed air as a gas to be supplied, the metal pipe material 14 at950° C. can be easily expanded by thermally expanded compressed air.

In parallel with this, the blow forming die 13 is further closed, and asshown in FIG. 7, the main cavity part MC and the sub-cavity parts SC1and SC2 are further narrowed between the lower die 11 and the upper die12.

Accordingly, the metal pipe material 14 is expanded in the main cavitypart so as to follow the recessed parts 16 and 24, and parts (both sideparts) 14 a and 14 b of the metal pipe material 14 are expanded so as toenter into the sub-cavity parts SC1 and SC2, respectively.

As shown in FIG. 8, the blow forming die 13 is further closed, and thusthe lower end surface 96 d of the protrusion 96 b of the upper dieholder 96 is brought into contact with the bottom surface 93 d of therecessed part 93 a of the lower die holder 93, the step surface 96 e ofthe upper die holder 96 is brought into contact with the upper endsurface 93 e of the protrusion 93 b of the lower die holder 93, and theinner surface of the protrusion 93 b of the lower die holder 93 and theouter surface of the protrusion 96 b of the upper die holder 96 arebrought into contact with each other. In a state in which the lower dieholder 93 and the upper die holder 96 are firmly adhered to each other,the closing of the blow forming die 13 is completed.

In this case, the main cavity part MC and the sub-cavity parts SC1 andSC2 are further narrowed than in the state shown in FIG. 7, and in thisstate, the sub-cavity parts SC1 and SC2 are blocked from the outside bythe inner surfaces 96 f of the protrusions 96 b of the upper die holder96 as described above.

Accordingly, the metal pipe material 14 softened by heating and suppliedwith the high-pressure gas is formed as the pipe part 100 a with arectangular cross-sectional shape following the rectangularcross-sectional shape of the main cavity part MC in the main cavity partMC, and formed as the flange parts 100 b and 100 c with a rectangularcross-sectional shape in which a part of the metal pipe material 14 isfolded in the sub-cavity parts SC1 and SC2.

In this blow forming, quenching is performed in such a way that theouter peripheral surface of the metal pipe material 14 expanded by beingsubjected to the blow forming is brought into contact with the recessedpart 16 of the lower die 11 so as to be rapidly cooled, andsimultaneously, brought into contact with the recessed part 24 of theupper die 12 so as to be rapidly cooled (since the upper die 12 and thelower die 11 have a large heat capacity and are managed at a lowtemperature, the heat of the pipe surface is taken to the dies at oncein a case where the metal pipe material 14 is brought into contact withthe dies.). Such a cooling method is referred to as die contact coolingor die cooling. Immediately after the rapid cooling, the austenite istransformed to martensite (hereinafter, transformation of austenite tomartensite will be referred to as martensite transformation). Since thecooling rate is reduced in the second half of the cooling, themartensite is transformed to another structure (troostite, sorbate, orthe like) owing to recuperation. Therefore, there is no need to performa separate tempering treatment. In this embodiment, in place of or inaddition to the die cooling, a cooling medium may be supplied to themetal pipe 100 to perform cooling. For example, the metal pipe material14 may be brought into contact with the die (upper die 12 and lower die11) to be cooled until the temperature is lowered to a temperature atwhich the martensite transformation starts, and then, the die may beopened and a cooling medium (gas for cooling) may be allowed to flow tothe metal pipe material 14 to cause the martensite transformation.

By the above-described forming method, the metal pipe 100 having thepipe part 100 a and the flange parts 100 b and 100 c can be obtained asa formed product as shown in FIG. 5. In this embodiment, since the maincavity part MC is configured to have a rectangular cross-sectionalshape, the metal pipe material 14 is subjected to the blow forming inaccordance with the shape, and thus the pipe part 100 a is formed into arectangular cylindrical shape. The shape of the main cavity part MC isnot particularly limited. In accordance with a desired shape, any shapemay be employed such as a circular cross-sectional shape, an ellipticalcross-sectional shape, or a polygonal cross-sectional shape.

According to this embodiment, in the expanding and forming of the metalpipe material 14 in the main cavity part MC and the sub-cavity parts SC1and SC2 communicating with the main cavity part MC in the blow formingdie 13, in a case where the material itself has a low strength, and thusthe metal pipe bursts due to the high-pressure gas and foreign mattersuch as fragments is generated in the blow forming die 13 (main cavitypart MC or sub-cavity parts SC1 and SC2), foreign matter moving outwardin the extending direction (horizontal direction in FIG. 8) of thesub-cavity parts SC1 and SC2 crossing the extending direction of themetal pipe material 14 is prevented from advancing by the protrusions 96b of the upper die holder 96 that is a shielding member provided on theextending line of the sub-cavity parts SC1 and SC2 in the expanding ofthe metal pipe material 14 and brought into contact with the sidesurfaces of the upper die 12. Accordingly, the foreign matter dischargedfrom the main cavity part MC or the sub-cavity parts SC1 and SC2 can besecurely prevented from scattering to the surroundings of the diewithout being discharged to the outside of the die.

In addition, the protrusion 96 b of the upper die holder 96 is providedto be brought into contact with the side surface of the upper die 12,and blocks the sub-cavity parts SC1 and SC2 formed between the lower die11 and the upper die 12 from the extending direction of the sub-cavityparts SC1 and SC2 when being moved with the movement of the upper die 12to close the blow forming die 13. Accordingly, the upper die holder 96functions as a shielding member and there is no need to provide aseparate shielding member. In addition, in a state in which the upperdie holder 96 serves as a shielding member and is released from the die,the upper die holder 96 is separated upward from the lower die 11together with the upper die 12. Accordingly, there is an advantage inthat for example, in a case where the metal pipe material 14 is insertedinto the lower die 11 or in a case where the formed metal pipe 100 isdetached from the lower die 11, the protrusion 96 b of the upper dieholder 96 does not become a hindrance. The upper die holder 96 havingthe protrusion 96 b is used as a shielding member since it is usedparticularly effectively as described above. However, the upper dieholder 96 may have no protrusion 96 b and the lower die holder 93 may beprovided with a protrusion that is brought into contact with the sidesurface of the lower die 11 and protrudes upward to function as ashielding member that blocks the sub-cavity parts SC1 and SC2 formedbetween the lower die 11 and the upper die 12 from the extendingdirection of the sub-cavity parts SC1 and SC2 in a case where the die isclosed.

FIG. 9 is a schematic diagram showing a configuration of a main part ofa forming device according to another embodiment of the invention.Another embodiment is different from the previous embodiment in that byusing an upper die holder 196 having no protrusion 96 b in place of theupper die holder 96 and using a lower die holder 193 having noprotrusion 93 b in place of the lower die holder 93, the sub-cavityparts SC1 and SC2 are not blocked by the die holders 193 and 196 fromthe extending direction of the sub-cavity parts SC1 and SC2 in a casewhere the blow forming die 13 is closed, and shielding plates 200, eachconstituting a shielding member, are provided at positions separatedfrom the side surfaces of the die on the extending line of thesub-cavity parts SC1 and SC2, respectively.

The shielding plate 200 is provided with a lower shielding plate 201,the length in an axial direction (length in a direction perpendicular tothe plane of FIG. 9) of which is almost the same as the length of theblow forming die 13 in the axial direction, that is erected on the lowerdie holder 94 and extends upward, and an upper shielding plate 202 thatis erected on the upper die holder 97 and extends downward.

In a state before the blow forming is started, the upper die 12 islargely separated upward from the lower die 11 (see FIG. 2). In thiscase, an upper part of the lower shielding plate 201 and a lower part ofthe upper shielding plate 202 does not overlap each other in ahorizontal direction shown in the drawing, crossing the metal pipematerial 14. In a state shown in the drawing in which the upper die 12is moved downward to start the blow forming, the upper part of the lowershielding plate 201 and the lower part of the upper shielding plate 202overlap each other in the horizontal direction shown in the drawing,crossing the metal pipe material 14, and the side surfaces thereof arebrought into contact with each other. In this state in which the sidesurfaces are brought into contact with each other, in a case where theupper die 12 is further moved downward, the lower part of the uppershielding plate 202 is further moved downward while overlapping with theupper part of the lower shielding plate 201.

According to another embodiment, in the expanding and forming of themetal pipe material 14 in the main cavity part MC and the sub-cavityparts SC1 and SC2 communicating with the main cavity part MC in the blowforming die 13, foreign matter such as fragments may be generated. Inthis case, the foreign matter moves outward in the extending directionof the sub-cavity parts SC1 and SC2 (horizontal direction in FIG. 9). Inaddition, the foreign matter is prevented from advancing by theshielding plates 200 provided on the extending line of the sub-cavityparts SC1 and SC2 in the expanding of the metal pipe material 14 andseparated from the side surfaces of the die. Accordingly, the foreignmatter discharged from the main cavity part MC or the sub-cavity partsSC1 and SC2 can be prevented from scattering to the surroundings of thedie, specifically, to a region outside the shielding plates 200, and canbe allowed to scatter only in a region inside the shielding plates 200(region where no worker approaches during the operation).

FIG. 10 is a schematic diagram showing a configuration of a main part ofa forming device according to a still another embodiment of theinvention. The still another embodiment is different from the previousembodiment in that shielding plates (shielding members) 300 having alower shielding plate 301 and an upper shielding plate 302, end parts ofwhich are brought into contact with each other, are used in place of theshielding plates 200 having the lower shielding plate 201 and the uppershielding plate 202 overlapping each other.

The lower shielding plate 301 is biased upward by a compression coilspring 303 and supported movably up and down by the lower die holder 94.The upper shielding plate 302 is biased downward by a compression coilspring 304 and supported movably up and down by the upper die holder 97.

In a state before the blow forming is started, the upper die 12 islargely separated upward from the lower die 11 (see FIG. 2) and an upperend part of the lower shielding plate 301 and a lower end part of theupper shielding plate 302 are separated from each other. However, in astate shown in the drawing in which the upper die 12 is moved downwardto start the blow forming, a protrusion 305 of the upper end part of thelower shielding plate 301 proceeds into and firmly adheres to a recessedpart 306 of the lower end part of the upper shielding plate 302.Accordingly, even in a case where the upper die 12 and the uppershielding plate 302 are moved downward from the state shown in thedrawing to close the blow forming die 13, the compression coil springs303 and 304 are compressed in the axial direction, and the state inwhich the protrusion 305 of the upper end part of the lower shieldingplate 301 proceeds into and firmly adheres to the recessed part 306 ofthe lower end part of the upper shielding plate 302 is maintained.

According to the still another embodiment, in the expanding and formingof the metal pipe material 14 in the main cavity part MC and thesub-cavity parts SC1 and SC2 communicating with the main cavity part MCin the blow forming die 13, foreign matter such as fragments may begenerated. In this case, the foreign matter moves outward in theextending direction of the sub-cavity parts SC1 and SC2 (horizontaldirection in FIG. 10). The foreign matter is prevented from advancing bythe shielding plates 300 provided on the extending line of thesub-cavity parts SC1 and SC2 in the expanding of the metal pipe material14 and separated from the side surfaces of the die. Accordingly, theforeign matter discharged from the main cavity part MC or the sub-cavityparts SC1 and SC2 can be prevented from scattering to the surroundingsof the die, specifically, to a region outside the shielding plates 300,and can be allowed to scatter only in a region inside the shieldingplates 300 (region where no worker approaches during the operation).

In place of the shielding plates 200 and 300 of the previousembodiments, a shielding member such as a shielding block may bedisposed to block the sub-cavity parts SC1 and SC2 from the outside ofthe die (in a direction crossing the extending direction of the metalpipe material 14) in a case where the block forming die 13 is closed.The shielding member such as a shielding block is provided at a positionseparated from the dies 11 and 12 so as not to block the sub-cavityparts SC1 and SC2 before closing of the die, and is moved to a positionto block the sub-cavity parts SC1 and SC2 in a case where the die isclosed. In addition, a part or the whole part of the shielding membersuch as a shielding block may proceed into the sub-cavity parts SC1 andSC2 to block the sub-cavity parts.

Although preferable embodiments of the invention have been described,the invention is not limited to the above-described embodiments. Forexample, the forming device may not essentially have the heatingmechanism 50, and the metal pipe material 14 may be heated in advance.

In the above-described embodiments, the upper die 12 is moved. However,in addition to or in place of the upper die 12, the lower die 11 may bemoved. In a case where the lower die 11 is moved, the lower die 11 andthe lower die holding part 91 are not fixed to the base 15, but attachedto the driving mechanism.

It should be understood that the invention is not limited to theabove-described embodiment, but may be modified into various forms onthe basis of the spirit of the invention. Additionally, themodifications are included in the scope of the invention.

What is claimed is:
 1. A forming device that expands a metal pipematerial to form a metal pipe, the device comprising: an upper die and alower die that form a main cavity part forming a main body part of themetal pipe and a sub-cavity part forming a flange part of the metal pipeby surfaces thereof opposed to each other; and a shielding member thatprevents foreign matter discharged from the main cavity part or thesub-cavity part from scattering, wherein the sub-cavity part is extendedto be opened to the outside of the die in a direction crossing anextending direction of the metal pipe material, and the shielding memberis provided on a line in which the sub-cavity part extends in theexpanding of the metal pipe material.
 2. The forming device according toclaim 1, wherein the shielding member blocks the sub-cavity part from adirection in which the sub-cavity part is extended.
 3. The formingdevice according to claim 2, wherein the shielding member is provided tobe brought into contact with a side surface of the upper die or thelower die and is moved with the movement of the upper die or the lowerdie to block the sub-cavity part from the direction in which thesub-cavity part is extended in a case where the die is closed.